Influence of Rapid Solidification on the Microstructural Development of Zinc-Aluminum Alloys

Crystal growth during rapid solidification was modeled, and the microstructure of rapidly solidified ZA48 alloy ribbon was analyzed. Results show that the solidification rate of a 50-μm-thick ribbon of ZA48 alloy is 1.06 × 105 K/s. At this high cooling rate, the microstructure consists of α-Al dendrites, η-Zn phase, and a large number of dispersed Mg32Al47Cu7 metastable phase. Rich Cu and Mg phases do not form as common casting alloy. Analysis of the rapid solidification process shows that the α-Al phase is the first to precipitate. Moreover, given that solute atoms cannot diffuse and rearrange at long ranges, precipitation of the equilibrium phase is restrained and the Mg32Al47Cu7 metastable phase is generated. © 2014 Springer Science+Business Media New York and ASM International.